1. Field of the Invention
The invention relates to an electronic part such as solid state image pick-up apparatus, light emitting apparatus, display apparatus, or the like and to a manufacturing method of such an electronic part. More particularly, the invention relates to an electronic part comprising a terminal of a functional element chip, a wiring member which is electrically connected to the terminal, and an adhesive material for adhering the functional element chip and a protecting member and to a manufacturing method of such an electronic part.
2. Related Background Art
Hitherto, as a kind of electronic part, an apparatus such that light information can be converted into an electric signal, the electric signal can be converted into the light information, light can be emitted or modulated by the electric signal, or an optical path can be changed by the electric signal has been known. An apparatus having functional elements has been known as such a kind of apparatus. As functional elements, a photosensitive element, a light emitting element, a DMD (Digital Micromirror Device), and the like have been known.
Among them, a solid state image pick-up apparatus having a photosensitive element array will be explained as an example of the electronic part. The solid state image pick-up apparatus is often provided in an image inputting apparatus such as video camera, digital still camera, or the like. According to such a solid state image pick-up apparatus, a photodiode serving as a photosensitive element, a CCD serving as a drive reading circuit, a CMOS, and the like are integrated on a semiconductor substrate such as a silicon wafer or the like, an integrated circuit is formed, and thereafter, a color filter and a microlens are formed above an image pick-up area (effective pixel area) by using an acrylic material or the like.
The silicon wafer on/over which the integrated circuit, color filter, and microlens have been formed is cut by performing a dicing process so as to obtain a chip. The resultant chip is enclosed in a ceramics package or the like. The chip and leads are electrically connected by a wire-bonding process or the like. After that, a protecting cap of a glass substrate is adhered onto the package, thereby protecting the chip against the ambient atmosphere.
In recent years, miniaturization of the image inputting apparatus such as a digital camera or the like has been progressed. Thus, it is also demanded to miniaturize and thin the solid state image pick-up apparatus. For example, the method of miniaturizing the solid state image pick-up apparatus has been disclosed in JP-A-7-099214.
FIG. 15 is a cross sectional view of a solid state image pick-up apparatus as an example of the conventional electronic parts. In FIG. 15, reference numeral 1 denotes a solid state image pick-up element chip; 2 a solid state image pick-up element; 3 a protecting cap; 4 a TAB (Tape-Automated Bonding) tape serving as a wiring and constructed by an insulative film 41 and a beam lead 42; 5 an electrode pad; 6 a bump; 11 an adhesive material; 12 an anisotropic conductive adhesive material; and 13 a sealing resin.
According to the solid state image pick-up apparatus shown in FIG. 15, first, the protecting cap 3 and TAB tape 4 are adhered via the light transparent adhesive material 11. The electrode pad 5 is formed on the solid state image pick-up element chip 1 having the solid state image pick-up element 2 and a microlens (not shown). Further, the bump 6 is formed on the electrode pad 5. The anisotropic conductive adhesive material 12 is coated onto the bump 6 and its peripheral areas by a dispenser or the like. The TAB tape 4 adhered to the protecting cap 3 by the adhesive material 11 is positioned to the solid state image pick-up element chip 1 and, thereafter, the bump 6 and TAB tape 4 are thermo-compression bonded. Thus, the solid state image pick-up apparatus shown in FIG. 15 is obtained.
Manufacturing steps of the conventional electronic part will be described with reference to FIGS. 16A to 16C. As an example of the electronic parts, the manufacturing steps of a prior art in which a gap between the solid state image pick-up element chip 1 and protecting cap 3 is held to be constant are shown here.
First, in FIG. 16A, reference numeral 13 denotes the solid state image pick-up element fixing tool; 14 a protecting cap holding tool; and 15 a gap control pin.
An explanation of the component elements having the same reference numerals as those described already is omitted here.
First, as shown in FIG. 16A, the solid state image pick-up element chip 1 to which the TAB tape 4 is electrically connected through the electrode pad 5 and bump 6 is put on the solid state image pick-up element fixing tool 13. The protecting cap 3 is fixed to the protecting cap holding tool 14. The gap control pin 15 is attached to the protecting cap holding tool 14.
Subsequently, as shown in FIG. 16B, the solid state image pick-up element fixing tool 13 and protecting cap holding tool 14 are overlaid. At this time, the gap control pin 15 is come into contact, with the solid state image pick-up element fixing tool 13 and the gap between the solid state image pick-up element chip 1 and protecting cap 3 is controlled.
In this state, as shown in FIG. 16C, outer peripheral portions of the solid state image pick-up element chip 1 and protecting cap 3 are sealed by a sealing resin 9.
(Technical Problem 1)
However, in the solid state image pick-up apparatus shown in FIG. 15, if a coefficient of thermal expansion of the solid state image pick-up element chip 1 and that of the protecting cap 3 are different, a distortion occurs in the solid state image pick-up element chip 1 due to heating in the manufacturing steps or due to a temperature change which is caused when the apparatus is used, or since a pressure of the air in the package changes due to the temperature change which is caused when the apparatus is used, a distortion occurs in the solid state image pick-up element chip 1. If the distortion occurs in the solid state image pick-up element chip 1, a focal position differs every pixel of the solid state image pick-up element 2 and picture quality deteriorates. In addition, there is also a case where the TAB tape 4 is peeled from the bump 6 due to a stress by such a distortion and the electric connection between the TAB tape 4 and solid state image pick-up element chip 1 is disconnected. Further, there is also a case where a phenomenon such that the protecting cap 3, adhesive material 11, TAB tape 4, and anisotropic conductive adhesive material 12 are peeled from each interface of the sealing resin 13 occurs.
(Technical Problem 2)
In the manufacturing steps of the solid state image pick-up apparatus shown in FIGS. 16A to 16C, since the control of the gap between the solid state image pick-up element chip 1 and protecting cap 3 is largely influenced by a variation of a glass thickness, a variation of a chip thickness, or precision of the tool, the gap cannot be accurately controlled. Specifically speaking, according to the conventional gap control using the gap control pin 15, although the gap between an upper surface of the protecting cap 3 (surface which does not face the solid state image pick-up element chip) and a lower surface of the solid state image pick-up element chip 1 (surface which does not face the protecting cap) is controlled, the gap between the surfaces of the protecting cap 3 and solid state image pick-up element chip 1, that is, the gap between the surfaces which face each other is not controlled- Therefore, if there is (are) a variation (variations) of the glass thickness or/and the chip thickness, the gap between the surfaces of the solid state image pick-up element chip 1 and protecting cap 3 which face each other cannot be held to be constant, so that a variation occurs. Consequently, reliability of the electric connection between the TAB tape 4 and solid state image pick-up element chip 1 cannot be assured. Thus, optical characteristics of the solid state image pick-up element 2 are adversely influenced. On the other hand, if it is intended to adhere the solid state image pick-up element chip 1 and protecting cap 3 while keeping the gap between the surfaces of them which face each other at high precision, high precision is required in a laminating apparatus, its construction becomes complicated, and the apparatus eventually becomes expensive.
It is, therefore, an object of the invention to improve electric reliability of an electronic part and cheaply provide an electronic part
Another object of the invention is to provide a cheap electronic part of high reliability while keeping a constant interval between a functional element chip and a protecting member.
In the specification, the gap between the surfaces of the solid state image pick-up element chip 1 and protecting cap 3 which face each other is simply referred to as a “gap” hereinbelow.
In the specification, the stress which causes a difference between the coefficients of thermal expansion of the solid state image pick-up element chip 1 and protecting cap 3 is simply referred to as a “stress” hereinbelow.